Effect of Vapor Pressure of H2O on the Formation of Nano-Crystalline TiO2 Ultrafine Powders

1999 ◽  
Vol 581 ◽  
Author(s):  
K. R. Lee ◽  
S. J. Kim ◽  
J. S. Song ◽  
S. Park
Keyword(s):  
Vapor Pressure ◽  
Reaction Rate ◽  
Ph Value ◽  
Anatase Phase ◽  
Rutile Phase ◽  
Precipitation Process ◽  
Nano Crystalline ◽  
Natural Decrease ◽  
Spontaneous Hydrolysis ◽  
Hydrolysis Of

ABSTRACTMono-dispersed TiO2 ultrafme particles with diameters 40-400nm were obtained from aqueous TiOCl2 solution with 0.67M Ti4+ concentration prepared diluting TiCl4 by homogeneous precipitation process in the ranges of 17-230°C. With the spontaneous hydrolysis of TiOCl2, which means the natural decrease of pH value in the aqueous solution, all mono-dispersed precipitates were crystallized with the anatase or rutile TiO2 phase. TiO2 precipitate with the pure rutile phase was fully formed at the temperatures below 65 °C, not involving the evaporation of H2O, and above 155 °C, which were available by suppressing it. TiO2 precipitate with rutile phase including a small amount of the anatase phase started to be formed in the intermediate temperatures above 70 °C showing the full formation of the anatase above 95 °C under the free evaporation of H2O. However, in the case of completely suppressing H2O evaporation at the temperatures above 70°C, TiO2 precipitate with anatase phase was fully transformed into the precipitate with the rutile phase by the vapor pressure of H2O. Therefore, the formation of TiO2 precipitates with the rutile phase around room temperature would be caused due to the existence of the capillary pressure between the agglomerated needle-shaped particles or the ultrafme clusters, together with the slow reaction rate.

Synthesis of Titania coated Alumina Particles by a Hybrid Sol-gel Method

2002 ◽  
Vol 740 ◽  
Author(s):  
A.D. Schmidt ◽  
S.B. Majumder ◽  
P.S. Dobal ◽  
R.S. Katiyar ◽  
D.C. Agrawal
Keyword(s):  
Anatase Phase ◽  
Sol Gel ◽  
Rutile Phase ◽  
Microscopy Imaging ◽  
Nano Crystalline ◽  
Heat Treated ◽  
Alumina Particles ◽  
Gel Technique ◽  
Titania Coatings ◽  
Titania Coating

ABSTRACTModifying their surface with a coating of another ceramic material can dramatically alter the properties of ceramic particles. In the present work we have demonstrated that the Al2O3 particles can be successfully coated by TiO2 using a novel sol-gel technique. The nature of these coatings was predicted on the basis of scanning electron microscopy imaging in conjunction with the micro-Raman scattering measurements. The surface morphology of these particles shows that either individual or group of sub-micron alumina particles are coated with the nano-crystalline titania particles. The thickness of the titania coating could be varied by changing the precursor sol concentration. Amorphous titania was converted to anatase phase at 400°C and upon further heating it started transforming to rutile phase, and both these phases coexisted in the coated particles that were heat treated up to 800°C. The mechanical strength of the titania coating was measured qualitatively by ultrasonicating the coated powders for longer duration to observe that titania coatings are strongly adhered with the alumina particles.

On the incorporation of nano TiO2 to inhibit concrete deterioration in the marine environment

2021 ◽  
Author(s):  
Zhen Li ◽  
Sufen Dong ◽  
Ashraf Ashour ◽  
Xinyue Wang ◽  
Vijay Kumar Thakur ◽  
...  
Keyword(s):  
Marine Environment ◽  
Silica Surface ◽  
Ph Value ◽  
Anatase Phase ◽  
Rutile Phase ◽  
Coarse Sand ◽  
Degree Of Polymerization ◽  
Nano Tio2 ◽  
Chemical Action ◽  
Biofilm Thickness

Abstract To develop high deterioration resistance concrete for marine infrastructures, two types of nano TiO2 (NT) including anatase phase NT and silica surface-treated rutile phase NT were incorporated into concrete. The fabricated NT modified concrete was then put into the marine environment for 21 months in this study. The effects and mechanisms of two types of NT on the deterioration of concrete in the marine environment were investigated from three aspects, including seawater physical and biological and chemical actions on concrete with NT. Under the seawater physical action, the exposed degree of coarse sand particles on the surface of control concrete is greater than that of concrete with NT. Owing to the microorganism biodegradation property of NT, the elimination and inhibition rates of concrete with NT on microorganisms can reach up to 76.98% and 96.81%, respectively. In addition, the surface biofilm thickness of concrete can be reduced by 49.13% due to the inclusion of NT. In the aspect of seawater chemical action, NT can increase the pH value inside concrete by 0.81, increase the degree of polymerization of C-S-H gel, and improve the interfacial transition zone between cement paste and aggregate in concrete. Compared to concrete with anatase phase NT, silica surface-treated rutile phase NT is more effective in improving the deterioration resistance of concrete in the marine environment. It can be concluded that incorporating NT can inhibit the deterioration of concrete in the marine environment.

Ultrafine TiO2 Powders Prepared from Aqueous TiCl4 Solutions at Room Temperature

2007 ◽  
Vol 353-358 ◽  
pp. 2135-2138
Author(s):  
Hong Liang Yi ◽  
Jie Zhang ◽  
Ming Tu Ma ◽  
Hao Zhang ◽  
Bong Ho Lee ◽  
...  
Keyword(s):  
Particle Size ◽  
Room Temperature ◽  
Ph Value ◽  
Anatase Phase ◽  
Average Particle Size ◽  
Rutile Phase ◽  
Average Particle ◽  
Spectral Peaks ◽  
Scherrer Formula ◽  
Stock Solutions

Ultrafine TiO2 powders as rutile and anatase phase were simply precipitated at room temperature for only tens of hours by simply controlling the pH value and Ti4+ concentration via aqueous TiCl4 solution. Under the optimal pH value and Ti4+ concentration, the average particle size of powders with rutile phase was 3.7nm, while that of powders with anatase phase was 3.0nm. The average particle size was calculated from the broadening of corresponding X-ray spectral peaks by Scherrer formula. In addition, 3.0 mol.l-1 are suggested to be used as concentration of stock solutions instead of the current concentration 2.0 mol.l-1.

Preparation of a new metallomicelle catalyst for the hydrolysis of bis(4-nitrophenyl) phosphate

2013 ◽  
Vol 67 (4) ◽  
Author(s):  
Jia-Qing Xie ◽  
Ci Li ◽  
Min Wang ◽  
Bing-Ying Jiang
Keyword(s):  
Reaction Rate ◽  
Active Species ◽  
Local Concentration ◽  
Catalytic Hydrolysis ◽  
Catalytic Function ◽  
Nitrophenyl Phosphate ◽  
Spontaneous Hydrolysis ◽  
Lauryl Ether ◽  
Hydrolysis Of ◽  
Bnpp Hydrolysis

AbstractA new metallomicellar system containing cerium(III), a macrocylic polyamine ligand, and the nonionic surfactant Brij35(polyoxyethylene(23) lauryl ether) was prepared and used as a catalyst in the hydrolysis of bis(4-nitrophenyl) phosphate (BNPP). Catalytic rate of the BNPP hydrolysis was measured kinetically using the UV-VIS spectrophotometric method. The results indicate that the metallomicellar system has relatively high stability and excellent catalytic function in the BNPP hydrolysis; also, the reaction rate of the BNPP catalytic hydrolysis increased by a factor of ca. 1 × 1010 compared to the BNPP spontaneous hydrolysis due to the catalytic effect of the active species and the local concentration effect of the micelles in the metallomicellar system. Experimental results also showed that the mono-hydroxy complex containing the macrocyclic polyamine ligand and cerium(III) is the real active species in the BNPP catalytic hydrolysis, and that the micelles provide a useful catalytic environment for the reaction. On basis of the research results, the reaction mechanism of BNPP catalytic hydrolysis has been proposed.

Kinetics and mechanism of alkaline hydrolysis of (Z)-O-(N-4-nitrophenylcarbamoyl)benzaldoximes in 30% aqueous ethanol

1979 ◽  
Vol 44 (8) ◽  
pp. 2401-2408
Author(s):  
Jaromír Mindl ◽  
František Radonský ◽  
Jiří Klicnar ◽  
Miroslav Večeřa
Keyword(s):  
Ir Spectra ◽  
Alkaline Medium ◽  
Alkaline Hydrolysis ◽  
Reaction Rate ◽  
Aqueous Ethanol ◽  
Hydrogen Ion ◽  
Neutral Medium ◽  
Spontaneous Hydrolysis ◽  
Hydrolysis Rates ◽  
Hydrolysis Of

Alkaline hydrolysis of (Z)-O-(N-4-nitrophenylcarbamoyl)benzaldoximes (I), the configuration of which was verified by IR spectra, produces a mixture of Z and E-benzaldoximates II and III, benzonitrile IV, and 4-nitrophenylcarbamate ion (V). In subsequent reactions II and III are hydrolyzed to benzaldehyde VI, and III and IV give finally benzoate VII. The carbamate V is decarboxylated to 4-nitroaniline (VIII). The compound I is hydrolyzed to oxime and 4-nitroaniline (VIII) in neutral medium. The hydrolysis rates of three compounds type I have been measured in 30% aqueous ethanol at pH 4 to 14. Character of the hydrolysis course in alkaline medium corresponds to a reaction of E1cB type. In neutral medium spontaneous hydrolysis with water takes place and the reaction rate is independent of concentration of hydrogen ion.

PREPARATION OF HOLLOW TIO2 NANOSPHERES FOR BIOMEDICAL APPLICATIONS

2016 ◽  
Vol 2 (2) ◽  
pp. 68-73
Author(s):  
Himani Kalita ◽  
Amita Pathak
Keyword(s):  
Anatase Phase ◽  
Thermal Studies ◽  
Rutile Phase ◽  
Titanium Tetraisopropoxide ◽  
X Ray Diffraction ◽  
Electron Microscopic ◽  
Templating Method ◽  
Microscopic Studies ◽  
Hydrolysis Of ◽  
Mn Concentration

The present work reports the preparation of hollow TiO2 nanospheres through sacrificial core templating method where, the sacrificial core of carbon spheres were indigenously synthesized and mixed into the starting ethanolic solution of titanium tetraisopropoxide (TTIP) under ambient condition. The solid obtained on the hydrolysis of TTIP were dried and calcined in air to acquire the hollow nanospheres of TiO2 in anatase phase. The acquired samples were further doped with varying mole % of Mn(II) to invoke magnetism in the material. X-ray diffraction and thermal studies reflected the anatase to rutile phase transformation of TiO2 at 550 °C when the dopant (i.e., Mn) concentration was increased from 0 to 6 mol % (with respect to Ti). The hollow and spherical morphology of the TiO2 nanostructures were confirmed through scanning electron microscopic studies while their ferromagnetic behaviour (at 300 K) was affirmed through SQUID analysis. For intracellular applications, the biocompatibility of the nanospheres was tested through conventional MTT assay, performed on MDA-MB 231 cancer cell lines.

Upgrading to nutrient removal by means of internal carbon from sludge hydrolysis

1994 ◽  
Vol 29 (12) ◽  
pp. 31-40 ◽  
Author(s):  
Pia Prohaska Brinch ◽  
Kim Rindel ◽  
Kathryn Kalb
Keyword(s):  
Reaction Rate ◽  
Wastewater Treatment Plants ◽  
Secondary Treatment ◽  
N Removal ◽  
Sludge Hydrolysis ◽  
Speed Up ◽  
On Line ◽  
Full Scale Tests ◽  
Biological Phosphorus ◽  
Hydrolysis Of

Due to the introduction of stricter nutrient effluent standards, many existing wastewater treatment plants performing only primary or secondary treatment are about to be upgraded. As the space available at the plants is, however, often limited, processes are required which will accommodate the need for increased treatment capacity without requiring much more space. In the hydrolysis of primary or pre-precipitated sludge direct-degradable organic carbon is produced which can speed up the reaction rate and increase both biological phosphorus and nitrogen removal. Full-scale tests with dosing of hydrolysate for biological P and N removal, respectively, have shown that this is a most viable process. The use of on-line monitoring has improved the process further.

Cyclization and acid-catalyzed hydrolysis of O-benzoylbenzamidoximes

1986 ◽  
Vol 51 (12) ◽  
pp. 2786-2797
Author(s):  
František Grambal ◽  
Jan Lasovský
Keyword(s):  
Reaction Rate ◽  
Kinetic Isotope ◽  
Acid Base Equilibrium ◽  
Mineral Acids ◽  
Kinetics Of Formation ◽  
Acid Catalyzed ◽  
Ph Scale ◽  
Kinetics Of ◽  
Hydrolysis Of ◽  
Derivatives Of

Kinetics of formation of 1,2,4-oxadiazoles from 24 substitution derivatives of O-benzoylbenzamidoxime have been studied in sulphuric acid and aqueous ethanol media. It has been found that this medium requires introduction of the Hammett H0 function instead of the pH scale beginning as low as from 0.1% solutions of mineral acids. Effects of the acid concentration, ionic strength, and temperature on the reaction rate and on the kinetic isotope effect have been followed. From these dependences and from polar effects of substituents it was concluded that along with the cyclization to 1,2,4-oxadiazoles there proceeds hydrolysis to benzamidoxime and benzoic acid. The reaction is thermodynamically controlled by the acid-base equilibrium of the O-benzylated benzamidoximes.

scholarly journals Synthesis of KAlSiO4 by Hydrothermal Processing on Biotite Syenite and Dissolution Reaction Kinetics

Minerals ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 36
Author(s):  
Jiangyan Yuan ◽  
Hongwen Ma ◽  
Zheng Luo ◽  
Xi Ma ◽  
Qian Guo
Keyword(s):  
Reaction Rate ◽  
Reaction Order ◽  
Dissolution Behavior ◽  
Precipitation Process ◽  
Hydrothermal Processing ◽  
Hydrothermal Conditions ◽  
Effective Utilization ◽  
Comprehensive Utilization ◽  
Dissolution Reaction ◽  
Significant Process

To make potassium from K-bearing rocks accessible to agriculture, processing on biotite syenite powder under mild alkaline hydrothermal conditions was carried out, in which two types of KAlSiO4 were obtained successfully. The dissolution-precipitation process of silicate rocks is a significant process in lithospheric evolution. Its effective utilization will be of importance for realizing the comprehensiveness of aluminosilicate minerals in nature. Two kinds of KAlSiO4 were precipitated in sequence during the dissolution process of biotite syenite. The crystal structures of two kinds of KAlSiO4 were compared by Rietveld structure refinements. The kinetics model derived from geochemical research was adopted to describe the dissolution behavior. The reaction order and apparent activation energy at the temperature range of 240–300 °C were 2.992 and 97.41 kJ/mol, respectively. The higher dissolution reaction rate of K-feldspar mainly relies on the alkaline solution, which gives rise to higher reaction order. During the dissolution-precipitation process of K-feldspar, two types of KAlSiO4 with different crystal structure were precipitated. This study provides novel green chemical routes for the comprehensive utilization of potassium-rich silicates.

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